* {
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Arial, sans-serif;
  background: linear-gradient(180deg, #f5f7fa, #e4e9f0);
  margin: 0;
  padding: 0;
}

.container {
  max-width: 480px;
  margin: 60px auto;
  background: #ffffff;
  padding: 28px;
  border-radius: 14px;
  box-shadow: 0 20px 40px rgba(0,0,0,0.08);
}

h1 {
  margin: 0;
  font-size: 24px;
  text-align: center;
}

.subtitle {
  text-align: center;
  color: #555;
  font-size: 14px;
  margin-bottom: 24px;
}

.form-group {
  margin-bottom: 16px;
}

label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 6px;
  color: #333;
}

input {
  width: 100%;
  padding: 12px;
  font-size: 15px;
  border-radius: 8px;
  border: 1px solid #d0d7de;
  transition: border 0.2s, box-shadow 0.2s;
}

input:focus {
  outline: none;
  border-color: #2563eb;
  box-shadow: 0 0 0 3px rgba(37,99,235,0.15);
}

button {
  margin-top: 12px;
  width: 100%;
  padding: 14px;
  background: linear-gradient(135deg, #2563eb, #1e40af);
  color: #fff;
  border: none;
  border-radius: 10px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.1s, box-shadow 0.1s;
}

button:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 20px rgba(37,99,235,0.35);
}

.result {
  margin-top: 18px;
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